Generally, semiconductor devices are used in a variety of electronic applications, such as computers, cellular phones, personal computing devices, and many other applications. Home, industrial, and automotive devices that in the past comprised only mechanical components now have electronic parts that require semiconductor devices, for example.
Semiconductor devices are manufactured by depositing many different types of material layers over a semiconductor workpiece or wafer, and patterning the various material layers using lithography. The material layers typically comprise thin films of conductive, semiconductive, and insulating materials that are patterned and etched to form integrated circuits (ICs). There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip, for example.
Optical photolithography involves projecting or transmitting light through a pattern comprising optically opaque areas and optically clear or transparent areas on a mask or reticle. For many years in the semiconductor industry, optical lithography techniques such as contact printing, proximity printing, and projection printing have been used to pattern material layers of integrated circuits. Lens projection systems and transmission lithography masks are used for patterning, wherein light is passed through the lithography mask to impinge upon a photosensitive material layer disposed on a semiconductor wafer or workpiece. After development, the photosensitive material layer is then used as a mask to pattern an underlying material layer. The patterned material layers comprise electronic components of the semiconductor device.
There is a trend in the semiconductor industry towards scaling down the size of integrated circuits to meet the demands of increased performance and smaller device size. However, as features of semiconductor devices become smaller, it becomes more difficult to pattern the various material layers because of diffraction and other effects that occur during a lithography process. For example, key metrics such as resolution and depth of focus of the imaging systems may suffer when patterning features at small dimensions.
A number of next generation techniques are being pursued to overcome these limitations, but most of them use different imaging techniques, tools, and technology. Abandoning more than 25 years of learning and development in optical lithography may not be cost effective and involves tremendous risks.
What are needed in the art are lithography systems and methods of manufacture thereof that overcome these limitations, while still retaining the benefits of current lithography tools and techniques.